The present invention relates to a novel producing method for aryl ether compound, more in detail relates to an environmentally harmonized producing method for aryl ether in gaseous or supercritical state of carbon dioxide.
In the field of conventional chemistry, the ordinary purpose of it is to provide useful substances to the market. During the progress to achieve above purpose, the effort to reduce the generation of by-products is carried out. However, since the correct evaluation for said by-products from the biological view point was not sufficiently made in those days, many by-products which are negative to the environment from the biological view point were discharged in natural environment.
Among above mentioned circumstance, from the careful observant eyes of the peoples who have ardent interests to the nature, the charge of a mode of life of living things becomes to be realized and many substances causing said changes are also becoming to be realized. That is, the fundamental change to the concept of chemical products is started to be arisen.
Namely, in the development of the technique to make harmless or to remove above-mentioned negative chemical substances, or in the process to produce useful well-known substances, the developments are becoming to be proceeded so as to produce the products which are gentle to the nature or the products which are biologically mimetic materials.
Concerning above-mentioned circumstance, in the field of synthetic chemistry, an effort has been made to design a synthetic process in which products to be wasted or by-products are not generated. Further, even if a case that a by-product is generated, the effort to minimize the influence of the by-product to living things has been carefully made. And, also for the substance to be used in a synthetic process, it is required to use the substance which does not easily cause a chemical accident. According to the above-mentioned understanding, the synthetic reaction using carbon dioxide which is harmless and inflammable, especially using supercritical carbon dioxide which has intermediate function between gas and liquid, as a reactive medium is recognized as a reaction which meets to above mentioned social requirement, and new reaction methods are going to be developed.
Concerning above-mentioned present conditions, in the synthesis of urethane, the inventor of this invention has already proposed the method for reaction of amine and alkyl halide in supercritical carbon dioxide under the presence of a base and onium salt [Chem. Commun., page 151 (2000)], which is similar to the synthetic condition of aryl ether of the present invention.
In the etherification reaction of phenols, the following method was disclosed in Japanese Patent Laid Open Publication 11-236344 published on Aug. 31, 1999). That is, an aromatic compound possessing at least one hydroxyl group on an aromatic ring and can possess a carboxyl group and/or hydrocarbiloxycarbonyl group and a lower alcohol are used as the starting materials, and the method to produce hydrocarbil ether of the aromatic compound by substituting a hydrogen atom of a hydroxyl group on the aromatic ring of said aromatic compound with a hydrocarbil group of lower alcohol is described. In said producing method, a method to react these compounds in the condition in which at least one of carboxylic acids becomes supercritical state in the presence of said aromatic compound, lower alcohol or carboxylic acid In said method, carbon dioxide is used as an inert medium together with argon and methane, however, the reaction temperature higher than the critical temperature of lower alcohol is needed and the yield of the reaction product does not exceed 50%. Further, since the starting materials are quite different from that of the present invention and acidic condition is required for the progress of reaction, said method does not teach the producing method of aryl ether of the present invention. Furthermore, said method does not teach an improved synthetic technology of the conventional producing method of aryl ether in organic solvent using hydroxydiarylethers and organic halogen as the starting materials.
In the meanwhile, aryl ether is a chemical compound used as the synthesis materials of various fields such as liquid crystal, medicines, agricultural chemicals, dyes, synthetic polymer or others. And at the producing process of it, it is popular to use phenols and halogenated alkyl or harmful alkyl sulfate, and harmful and inflammable organic solvent. The wasted organic solvent after used, have a problem to cause an environmental problem when it is discharged.
Therefore, the object of the present invention is to provide a novel improved synthetic technique for producing aryl ether using hydroxyaryls and organic halogen as the starting materials. In the earnest investigation to accomplish said object, the inventor of the present invention has thought of the use of gaseous carbon dioxide or supercritical carbon dioxide which are the environmentally harmonized type fluid as a medium for reaction instead of the use of above mentioned organic liquid state medium. And the inventor of the present invention has investigated to design a system of reaction which allows the synthesis of the aimed compound using above mentioned starting materials in above mentioned medium. In the process of the investigation, the inventor of the present invention has concerned to apply the reactive condition which is proposed by the inventor of the present invention in above mentioned document. That is, said condition is used in the reaction using organic halogenated compound as one starting material and characterizes to make exist a base and onium salt by catalytic amount in the reaction system. By the substantial experiments, the inventor of the present invention have found that there is a reactive condition to produce aryl ether in above mentioned reactive condition, and accomplished the present invention.
The present invention is a method for producing an aryl ether produced by binding an aryloxy of hydroxyaryl with an organic group of organic halogen, which comprises reacting hydroxyaryl with organic halogen in gaseous carbon dioxide or supercritical carbon dioxide in the presence of base and onium salt. Desirably the present invention is the method for producing of said aryl ether which uses the onium salt by catalytic amount. More desirably, the onium salt is the compound represented by general formula of R1R2R3R4N+Xxe2x88x92 or R1R2R3R4P+Xxe2x88x92 (wherein R1, R2, R3, R4 respectively indicate a substituted or an un-substituted alkyl group, a cyclo-alkyl group, an alkenyl group, a cyclo-alkenyl group, an aryl group, an aralkyl group, an aralkenyl group, an alkenaryl group or an alkaryl group. R1, R2, R3, R4 can be same or can be different, and one to three of them can be a hydrogen atom. X indicates a halogen atom, a hydroxyl group, a hydrogensulfate group, a hydrogenphosphate group, a hydrogenphosphite group or a hydrophosphite group.). Further desirably, the present invention is the method for production of aryl ether wherein the base is a carbonate salt or a phosphoric salt of alkali metal or alkali earth metal (more than 2 can be used together with).